1. Field of the Invention
The present invention relates to a plasma processing apparatus used in manufacturing semiconductor devices or liquid crystal displays, the plasma processing apparatus being employed as an apparatus for etching or depositing films by means of a plasma generated through excitation by microwave.
2. Description of the Background Art
A plasma processing technique which uses the microwave is applied to a process of manufacturing a semiconductor or TFT (Thin Film Transistor) liquid crystal substrate. This plasma processing technique is now in wide use because of a high plasma density as well as easy control of ion energy.
It is generally difficult, however, to uniformly generate the plasma over a large area. In addition, with recent increase in demand for semiconductor and TFT liquid crystal substrates as well as increased size of process substrates, a demand for a higher production efficiency and a demand for technique of uniform plasma-processing for a large-sized substrate are growing.
In order to satisfy such demands, some plasma processing apparatuses use a slot plate. A plasma processing apparatus using a slot plate is described below in conjunction with FIG. 10.
FIG. 10 shows a structure of a conventional plasma processing apparatus employing a slot plate, the structure being shown in a cross section in the direction of the shorter side of a waveguide. Referring to FIG. 10, a chamber body 102 has a top chamber lid 101 placed via an O ring 109 to seal a process chamber 106 and keep a vacuum within process chamber 106. A substrate holder 107 on which a substrate to be processed (hereinafter substrate) 108 is placed is provided in process chamber 106. Further, a rectangular microwave entrance window 111 made of such a dielectric as alumina is formed in top chamber lid 101 via an O ring 110.
Onto the vacuum side of top chamber lid 101, a dielectric plate 115 is fastened by a dielectric plate fastening member 116. Microwave entrance window 111 and dielectric plate 115 are fastened to contact each other. A vacuum is created in process chamber 106 by removing air from an opening 102a in the bottom of chamber body 102 by means of a vacuum pump (not shown). Chamber body 102 further has a gas inlet 105 provided for taking in a reactant gas.
A waveguide 103 is placed on top chamber lid 101. A microwave generator (not shown) is connected to waveguide 103. A metal slot plate 104 having a plurality of slots 104a is provided between microwave entrance window 111 and waveguide 103.
Referring to FIG. 11, rectangular slots 104a are formed in a region corresponding in position to an opening of waveguide 103. Slots 104a are accordingly placed between the waveguide opening 103a and microwave entrance window 111. Slots 104a are positioned and sized appropriately so that a uniform plasma process is achieved under a certain process condition.
When this conventional plasma processing apparatus is operated, microwave is generated by the microwave generator (not shown), supplied through waveguide 103, slots 104a of slot plate 104 and microwave entrance window 111, and radiated from dielectric plate 115 into process chamber 106, in order to change a reactant gas supplied from gas inlet 105 into a plasma. The plasma thus excited is used to plasma-process substrate 108. As the slots 104a are positioned and sized most appropriately, substrate 108 is uniformly processed by the plasma.
In recent years, such multilayer films as two-layer and three-layer films have been used each as a material of a liquid crystal or semiconductor device. In addition, respective areas of liquid crystal substrates and semiconductor wafers have been increasing. Accordingly, a large-area workpiece formed of various types of films is often processed uniformly by a plasma successively in the same process chamber. Problems of such a process are described below in connection with a dry etching process.
Suppose that films made of different materials are to be etched or films made of the same material require different etching performances (e.g. shape, selectivity). Then, a process gas, an etching mode and an etching apparatus appropriate for each film must be selected, resulting in decrease of versatility of the apparatus.
Suppose that a film constituted of stacked layers of different materials is to be etched. If an apparatus and a condition that are most suitable for any layer of a certain material are selected in terms of the best uniformity, the best uniformity could not be achieved for other layers of materials different from that certain material. Consequently, a favorable uniformity cannot be achieved for the entire stacked-layer film.
Moreover, when isotropic etching and anisotropic etching are combined for etching a material into a desired shape, different process conditions, process gases for example, are necessary. In such a case, under significantly different conditions, it is difficult for a microwave plasma source to allow various materials on a large-area substrate or wafer to be etched into desired shapes by using one slot pattern.
One object of the present invention is to provide a plasma processing apparatus keeping the uniformity in a plasma process under significantly different process conditions, for example, when films of different materials on a large-area substrate or wafer are to be processed or a film composed of stacked layers of different materials is to be processed.
According to the present invention, a plasma processing apparatus includes a process chamber, a microwave generating unit, a waveguide, a slot plate and a slot plate drive unit. The process chamber has a wall partially formed of a microwave entrance window made of a dielectric, for performing a plasma process in the process chamber. The microwave generating unit generates microwave. The waveguide supplies the microwave generated by the microwave generating unit into the process chamber via the microwave entrance window. The slot plate has a slot-formed region for passing the microwave from the waveguide to the microwave entrance window. The slot plate drive unit drives the slot plate to change the position of the slot plate with respect to the microwave entrance window. The slot-formed region has openings through which the microwave is passed, and the slot plate is moved with respect to the microwave entrance window to change at least one of the position, number and area of the openings of the slot-formed region.
The plasma processing apparatus of the present invention has the slot plate moved with respect to the microwave entrance window so that at least one of the position, number and area of the openings, which pass the microwave therethrough, of the slot-formed region of the slot plate can be changed. Then, for each process, the most appropriate state of the slot openings is provided. The process is thus carried out uniformly with stability.
With regard to the plasma processing apparatus, preferably the slot-formed region has a plurality of slots formed per the microwave entrance window and arranged in the direction in which the slot plate is moved, and the slot plate is moved to select, from those slots, slots passing the microwave and slots passing no microwave.
Accordingly, the most appropriate slots can be selected from a plurality of slots for each process so that the process can be carried out under the optimum condition.
With regard to the plasma processing apparatus, preferably the microwave entrance window has an open face in the shape of a rectangle on the wall of the process chamber, the slot plate is movable in the direction of the shorter side of the rectangle and, from those slots arranged in the direction of the shorter side, slots passing the microwave and slots passing no microwave are selected.
The slot plate is thus moved in the direction of the shorter side of the open face to select appropriate slots, which means that the distance of movement of the slot plate is shorter than that when the slot plate is moved in the direction of the longer side of the open face.
With regard to the plasma processing apparatus, preferably the slot plate is moved to change the slots passing the microwave, when plasma processes are successively performed on one and the same workpiece under a plurality of process conditions.
The most appropriate state of the slot openings is provided for these process conditions. The processes are thus carried out uniformly with stability.
Preferably, the plasma processing apparatus is used for processing the workpiece having stacked films by plasma.
As the processes are carried out uniformly with stability, each of the stacked films can be processed under the optimum condition.
With regard to the plasma processing apparatus, in the slot-formed region, a slot is preferably formed having its opening changed in at least one of the area and position with respect to the direction in which the slot plate is moved.
The state of the slot opening is thus controlled by moving the slot plate.
With regard to the plasma processing apparatus, preferably a plurality of microwave entrance windows are arranged in the form of a matrix in parallel with each other on the wall of the process chamber.
The state of slot openings can thus be controlled over a wide range in the process chamber.
In the plasma processing apparatus, preferably the slot plate and the slot plate drive means are provided per the waveguide.
Then, the state of slot openings can be controlled for each waveguide.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.